I did a little chrono work the other day, and thought I would share my results.

17 Feb 06
Temp: 68* and sunny
Chrono 10' from muzzle

16" DPMS M4gery

Rem UMC 55gr FMJ     2873  2873  2842  2855  2812  2855  2873  2861
Avg:  2855      SD:  20.7

WCC '86 (Q3131?)   3065  2976  3016  2969  2996
Avg:  3004      SD:  38.5

PMP South African 55gr FMJ     2989  2962  3009  2930  2949
Avg:  2967      SD:  31.4

IMI 5.56 (Q3131 spec?)     2861  2911  2836  2886  2830
Avg:  2864      SD:  34.05

Wolf 62gr Polymer     2704  2704  2699  2635  2699
Avg:  2688      SD:  29.8
***throw out low velocity (2635)***
Avg:  2701      SD:  2.8

WCC Q3131A 55gr     3086  3125  3115  3086  3129
Avg:  3108      SD:  20.8

WCC Q3131 55gr     3115  3122  3108  3079  3065
Avg:  3097      SD:  24.5

Malaysian M193 '84     3137  3182  3167  3174  3212
Avg:  3174      SD:  27

Winchester White Box 45gr HP     3267  3182  3244  3079  3100
Avg:  3174      SD:  83.8  *highest recorded


18" Armalite DCM barrel

Malaysian M193 '84     3236  3212  3226  3220  3252
Avg:  3229      SD:  15.4

Wolf 62gr Polymer     2732  2754  2754  2818  2836
Avg:  2778      SD:  45

WCC '86     3037  3093  3129  3129  3100  3079  3030  3100  3093  3065
Avg:  3085      SD:  33

Winchester White Box 45gr HP     3252  3228  3197  3212  3252  3392  3401  3292
Avg:  3278      SD:  78

Average accuracy was around 2" for just about all the loads.  The most accurate load was the Winchester White Box 45gr HP's, which also had the highest standard deviation.  The most inaccurate load was the Malaysian M193, which consequently had the highest average muzzle velocity.  One interesting note is the Wolf Polymer, which I've chrono'd before and recorded single digit standard deviations in the past.  However, accuracy was and still is mediocre.  

Another interesting note is the SD's of the ammo stayed fairly consistent between the 16" and 18" barrels, and acuracy was similar in both guns.  However, the best group was around 3/4" with the 45gr HP's in the 18" DCM barrel.

What was the twist rate on the barrels, or are you gonna make me look it up?

Damn, didn't even think about that.  The DPMS has a 1/9 and the Armalite is a 1/8" twist.

I have some data to add. I can't figure out why XM193 is so hot out of my gun. I'm thinking it might be a hot LOT# of LC or something.



Rifle: Colt 6520, 16", 1/7, chrome lined chamber & bore. M16 carrier.
Chrono: Alpha Master Chrony.
Setup: 10ft from muzzle.
Weather: 79, sunny. Elevation less than 100ft. Slightly humid.


Federal XM193 55gr LOT-105

       3294
3212
3268
3246
3225

Average: 3249
SD:         33


Chrono reads perfect with all other calibers. Barrel was not hot on the Colt. Rounds were not left in chamber to cook. I thought a 16" was suppose to be 100-120fps less than these numbers?

Damn thats some hot ass lc.

Yeah I know, I am starting to get concerned. There were no pressure signs on the brass or primer, none at all. Maybe I am just being paranoid. Either way, it is kinda cool to get rifle velocities out of a carbine.


Maybe someone who's an expert will post knowing something  I don't.

Sounds like you have a good load going.  How accurate has it been?

?

Good report, thanks for sharing.

Thank you for sharing!!!

No problem.  I'm working on a trade for a 24" Savage right now, so I should be able to post velocities out of a 24" tube before long.  

Quoted: I can't figure out why XM193 is so hot out of my gun. I'm thinking it might be a hot LOT# of LC or something.

Since these are from Lake City and made to meet U.S. military specs, it could be the bullet jacket allowing higher velocity: lower friction.  Other than that possibility, you may have one HOT lot.  

Quoted: One interesting note is the Wolf Polymer, which I've chrono'd before and recorded single digit standard deviations in the past.  However, accuracy was and still is mediocre.

Several high masters I know shoot Russian primers specifically because the primers are extremely consistant: better than Federal Gold or CCI Bench Rest.  I've seen strings of 10 shots, in .308, giving a standard deviation in the low teens and single digits, using an Ohler 35.

Russian bulk bullets are not known for accuracy; its all about high numbers and full auto.  Russian match bullets are some of the best...when you can FIND them outside of Mother Russia.

Side note:
I wish that we could import Swiss GP90 again, and get Finn 5.56mm.  Those two countries believe in very accurate issue ammo.

Thanks for your work.  It is not easy taking the time to set up a chrono and shoot for it: takes a long time.

Here's some results I dug up from a shoot back in December (some from a 22" barrel).

Barrel Length: 16.5"
Temperature: 48*
Chrono 12 feet from muzzle

Malaysian M193, '84 Head stamp (16.5" bbl)
3074 3086 3065 3058
avg: 3071
SD: 12.09
med: 3069.5

Malaysian M193, '84 Head stamp (22" bbl)
3276 3292 3252
avg: 3273
SD: 20
med: 3276

Accuracy was around 1.75-2" @ 100 yards


Winchester Q3131
3037 2987 3044
avg: 3022
SD: 31
med: 3037

South African PMP .223
2801 2766 2812
avg: 2793
SD: 24
med: 2801

Wolf Polymer
2666 2666 2661
avg: 2664
SD: 2.8
med: 2666